1. Field of the Invention
The invention relates to the supervision of errors (or "disturbances") in industrial processes and, more particularly, to disturbance supervision algorithms used in the operation of telecommunications exchanges.
2. History of the Prior Art
Errors periodically occur in virtually every industrial process known to man. Thus, most mechanized processes include some way to detect the occurrence of errors in order to call them to the attention of an operator when required. The significance of an error within a process is determined by the nature of the error as well as the frequency with which such errors occur. Moreover, in complex industrial complexes such as those performed by telecommunications switching exchanges and digital computers, such occurrences are generally referred to as a disturbance, simply indicating the occurrence of an anomalous event within the process. For example, a disturbance can be a parity error during the exchange of data, or a sporadic hardware fault within the system. Other examples of abnormal events within such systems referred to as disturbances include:
a. A cyclic redundancy check (CRC) error; PA1 b. Congestion within the system; PA1 c. The occurrence of a greater number of bit errors in a particular time frame than the bit correction algorithm can cope with; PA1 d. Software exceptions within the system; and PA1 e. Data inconsistencies detected during runtime. PA1 a. Paper getting stuck in a copying machine; PA1 b. The misfiring of cylinders in an engine; and PA1 c. The occurrence of a false result in a blood test. PA1 a. The mathematics for analyzing disturbances have a number of special characteristics at low disturbance frequencies; and PA1 b. The mathematics break down for high disturbance frequencies. PA1 a. The size of the bucket; PA1 b. The size of the hole in the bottom (which is generally normalized to one); and PA1 c. The size of the cup used in filling the bucket. The size of the bucket is the difference in height between the ceiling and the floor. The size of the step is called the disturbance step.
Single disturbances within such systems produce any need for the raising of an alarm; but when disturbances become too frequent within a system, a technician should generally be notified so as to be able to take remedial action to prevent system failure. Moreover, it is generally the number of disturbances as a proportion of the number of events during which a disturbance could possibly occur which is of most interest to an operator of a process, e.g., five disturbances within the sequence of one hundred events is of much greater interest than ten disturbances during the occurrence of a million such events. The monitoring and measurement of the number of disturbances which occur during a sequence of events and the production of an alarm when the number of disturbances become too great is known as disturbance supervision.
The concepts of disturbance and disturbance supervision are applicable to virtually all fields of industrial processing. In principle, any event, the occurrence of which is undesirable but not in itself sufficient reason to raise an alarm, can be classified as a disturbance. Only when the frequency of these undesirable events becomes "too high" in some sense or another is it desired to raise an alarm. Other examples of disturbances within industrial processors could include:
In general, however, the analysis of disturbance alarm supervision in accordance with the principle of the present invention relates principally to disturbance frequencies which are no greater than about one percent of the frequency of normal events. This restriction is for basically two reasons: